1. Field of the Invention
The invention relates to the blade guide of a crank shear or guillotine shear for flying transverse parting of strips, particularly steel strips. The shear having a shear housing in which blades fastened to blade supports are movable relative to one another on parallel guide paths for cutting and transversely to the guide paths in the running direction of the strip and at the running speed of the strip.
2. Description of the Prior Art
For transverse severing of continuously moving strips, shears are used in which the blades move at the same speed as the strip to be cut when cutting in the running direction of the strip. Various systems such as drum shears, guillotine shears or pendulum shears are known. Each of these systems has its own advantages or disadvantages which will not be discussed at greater length here.
Guillotine shears of the generic type have two problems to be emphasized, namely the relatively large mass of the shears to be guided in and out of the cutting position and the adjustment of the blades and blade gaps relative to the strip to be cut.
A guillotine shear with a stationary upper blade is known from the German Offenlegungsschrift 26 55 962. The lower blade of this guillotine shear is movable toward the upper blade in parallel guide paths and the entire shear housing is in turn displaceable on a horizontal path in accordance with the running speed of the strip. The movable blade is driven by an adjustable crank mechanism and is brought into a cutting position on the continuously running strip corresponding to the desired cutting length.
In the known construction, tile heavy shear housing is moved independently of the drive of the movable blade, but it is very difficult to accelerate and brake the large masses, so that correspondingly dimensioned drives are required. An adjustment of the blades for severing strips of different thickness is not described in this previously known solution. However, from prior art it is known to one skilled in the art to adjust the guides of the blade support via wedges, which is complicated and difficult to do, since everything rotates in guillotine shears, particularly those with movable upper and lower blades. It is also known to displace the helical-geared drive gears axially on the crankshaft so as to produce rotation between the drive crankshafts. However, this is problematic in rapidly moved shears, particularly those working in start-stop operation, since the one-sided helical gearing causes high axial forces.
Finally, it is known to construct one of the blade supports so that it can be rotated in the cutting plane. This construction changes the parallel state of the blades, weakens the blade beam, and drastically increases the weight of the rotating mass.